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From:   "Sungjong Seo" <sj1557.seo@samsung.com>
To:     "'Tetsuhiro Kohada'" <kohada.t2@gmail.com>
Cc:     <kohada.tetsuhiro@dc.mitsubishielectric.co.jp>,
        <mori.takahiro@ab.mitsubishielectric.co.jp>,
        <motai.hirotaka@aj.mitsubishielectric.co.jp>,
        "'Namjae Jeon'" <namjae.jeon@samsung.com>,
        <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>
In-Reply-To: <8a430d18-39ac-135f-d522-90d44276faf8@gmail.com>
Subject: RE: [PATCH 2/3] exfat: remove useless check in exfat_move_file()
Date:   Mon, 28 Sep 2020 16:36:28 +0900
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References: <CGME20200911044511epcas1p4d62863352e65c534cd6080dd38d54b26@epcas1p4.samsung.com>
        <20200911044506.13912-1-kohada.t2@gmail.com>
        <015f01d68bd1$95ace4d0$c106ae70$@samsung.com>
        <8a430d18-39ac-135f-d522-90d44276faf8@gmail.com>
Precedence: bulk

> >> --- a/fs/exfat/namei.c
> >> +++ b/fs/exfat/namei.c
> >> =40=40 -1095,11 +1095,6 =40=40 static int exfat_move_file(struct inode
> >> *inode, struct exfat_chain *p_olddir,
> >>   	if (=21epmov)
> >>   		return -EIO;
> >>
> >> -	/* check if the source and target directory is the same */
> >> -	if (exfat_get_entry_type(epmov) =3D=3D TYPE_DIR &&
> >> -	    le32_to_cpu(epmov->dentry.stream.start_clu) =3D=3D p_newdir->dir=
)
> >> -		return -EINVAL;
> >> -
> >
> > It might check if the cluster numbers are same between source entry
> > and target directory.
>=20
> This checks if newdir is the move target itself.
> Example:
>    mv /mnt/dir0 /mnt/dir0/foo
>=20
> However, this check is not enough.
> We need to check newdir and all ancestors.
> Example:
>    mv /mnt/dir0 /mnt/dir0/dir1/foo
>    mv /mnt/dir0 /mnt/dir0/dir1/dir2/foo
>    ...
>=20
> This is probably a taboo for all layered filesystems.
>=20
>=20
> > Could you let me know what code you mentioned?
> > Or do you mean the codes on vfs?
>=20
> You can find in do_renameat2(). --- around 'fs/namei.c:4440'
> If the destination ancestors are itself, our driver will not be called.

I think, of course, vfs has been doing that.
So that code is unnecessary in normal situations.

That code comes from the old exfat implementation.
And as far as I understand, it seems to check once more =22the cluster numb=
er=22
even though it comes through vfs so that it tries detecting abnormal of on-=
disk.

Anyway, I agonized if it is really needed.
In conclusion, old code could be eliminated and your patch looks reasonable=
.
Thanks

Acked-by: Sungjong Seo <sj1557.seo=40samsung.com>

>=20
>=20
> BTW
> Are you busy now?
I'm sorry, I'm so busy for my full time work :(
Anyway, I'm trying to review serious bug patches or bug reports first.
Other patches, such as clean-up or code refactoring, may take some time to =
review.

> I am waiting for your reply about =22integrates dir-entry getting and
> validation=22 patch.
As I know, your patch is being under review by Namjae.

>=20
> BR
> ---
> Tetsuhiro Kohada <kohada.t2=40gmail.com>